Commonly used calorimetric flow sensors feature a heat source in form of a heater and spatially separated temperature sensors embedded in a thin membrane. The temperature sensors typically located upstream and downstream of the heater measure the amount of heat that is carried away by the fluid in a direct or indirect way. A thermocouple may be used as temperature sensor which thermocouple is made from two dissimilar materials which are joined at at least one junction. The junction is located on the membrane whose temperature condition is to be measured. This junction is also referred to as hot junction. Terminals of the thermocouple, or further junctions/cold junctions when connecting to other thermocouples are maintained at a constant temperature of the bulk material surrounding the membrane, for example. A difference in potential is created whenever there is a difference in temperature between the hot junction of the respective thermocouple and the corresponding cold junction, resulting in an easily measurable thermoelectric voltage. The difference between the up- and downstream thermoelectric voltage can be used as a measure for a velocity of the fluid.